Data transmission system



oct. 7, 1947. 5|NGER 2,428,389

DATA TRANSMISS ION SYSTEM Filed Dec. 21, 1942 2 Sheets-Sheet 1 lNVENTO/P E J SINGER ()AnECL-MLQ AT7UAWEV Oct. 7, 1947. J, s' 2,428,389

DATA TRANSMIS S ION SYSTEM Filed Dec. 21, 1942 2 Sheets-Sheet 2 FIG. 2

CARR/ER FREQUENCY SUPPLY 6C7.

AZ/MUTH GEAR INVENTOR f. J. SINGER A TTORNEV Patented Dot. 7, 1947 2,428,389 DATA TRANSMISSION SYSTEM Fred J. Singer, Rockville Centre,

N. Y., assignor to Bell Telephone Laboratories, Incorporated,

New York, N. Y., a corporation of New York Application December 21, 1942, Serial No. 469,682

8 Claims. 1

This invention relates to data transmission systems. More particularly, this invention is a data transmission system in which alternating currents of different frequencies are transmitted between stations to define the data.

An object of this invention is the improvement of data transmission systems.

A more particular object of this invention is the provision of a data transmission system in which alternating currents of different frequencies are employed to identify observed data.

station to identify data observed at the observing station.

A further feature of this invention is an arrangement in which alternating current of fifteen different frequencies is employed. Current of eac said frequencies is conducted from said phantom circuit through a first selecting device at the observing station and returned to the receiving station over one of said physical circuits to idenquencies from the receiving station to the observing station for purposes of defining observations and direct current as well as to energize apparatus employed at the transmitting station.

A further feature of this invention is an arrangement wherein part of the signals defining the observed data is impressed on a motor switch at the receiving station which in turn controls an indicator so that it moves progressively or retrogressively in single steps as each signal is received. The range of such indicator may be unlimited but is adapted in this embodiment to defining any of three hundred and sixty observations corresponding to three hundred and sixty degrees.

These and other features will be apparent from the following description when read with reference to the associated drawings, in which:

Fig. 1 represents the apparatus associated with an observing station; and

Fig. 2 represents the apparatus associated with a receiving station.

The invention herein has wide application. In the present embodiment it is arranged particularly to define angles between a base-line and the line of sight to a target. The angle between the base-line and the target is established by rotating a telescope on an azimuth instrument until the line of sight through the telescope extends to the target. The position of the target is established by means of two telescopes, one located at each extremity of the base-line. The length of the base-line, which is fixed, and the size of the two angles between the base-line and the two lines of sight to the target fix the position of the target.

In such an arrangement two observing equipments, such as Fig. l, and two receiving equipments, such as Fig. 2, are required. The observing equipment at each observing station would be identical with Fig. 1. The receiving equipment associated with each observing station would be identical with Fig. 2. In the description to follow the operation of the equipment at one observing station and its associated equipment at the receiving station will be described. The same description would apply to the second observing station and its associated equipment.

Refer to Figs. 1 and 2. At the receiving station, as shown in Fig. 2, a source of alternating current 20l of fifteen different frequencies is connected to winding 202 of transformer 203. The top terminal of the winding 204 of transformer 203 is connected to the mid-point of winding 205 of transformer 206. The bottom terminal of winding 204 of transformer 203 is connected to the mid-point of winding 20'! of transformer 208. The top and bottom terminals of the winding 205 Of transformer 206 are connected by means of two conductors 209 and 2 ID to the top and bottom terminals of winding |0| of transformer I02 at the observing station. The top and bottom terminals of the secondary 201 of transformer 203 are connected by means of conductors 2H and 2I2, respectively, to the top and bottom terminals of winding I03 of transformer I04 at the observing station. The mid-point of winding IOI of transformer I02 is connected to the top terminal of winding I65 of transformer I06. The mid-point of winding I03 of transformer I04 is connected to the bottom terminal ofwinding I01 of transformer I06.

The impedance of the circuit connecting the top terminal of winding 204 of transformer 203 to the top terminal of winding I05 of transformer I33 is equal to the impedance of the circuit connecting the bottom terminal of winding 264 of transformer 203 to the bottom terminal or winding I05 of transformer I06. Each of these circuits forms one side of a phantom circuit.

The fifteen carrier frequency currents impressed on winding 204 in Fig. 2 at the receiving station are impressed across Winding I05 in Fig. 1 and induced in winding I08. A source of direct current 2I3 is connected through variable resistor 2I4 to the mid-point of winding 204. The four conductors 269, 2I0, 2H and 2I2 serve as parallel conductors for the direct current. The parallel branches join and the circuit extends through a single conductor I09 and through the internal connections of amplifier III] to ground. The direct current source 2I3 at the receiving station serves as a battery supply for amplifier The fifteen alternating frequency currents are amplified in amplifier III) and impressed on parallel conductors III and H2. Conductors Hi and H2 are connected in parallel to thirty band-pass filters I20 to I49. Each one of the fifteen bandpass filters I20 to I34 in the upper portion of the drawing is arranged to pass current of a different particular one of the fifteen frequencies and to suppress current of the fourteen other frequencies. Each one of the fifteen band-pass filters I35 to 4 bottom terminal of winding I54 of transformer Depending upon the position of rotatable arm I62 of switch I55, the circuit from some one of band-pass filters I40 to I49 will be closed through conductor I63 and conductor I6I t0 the bottom terminal of winding I54 of transformer I04.

The position of each of rotatable arms I56, I53 and I 62 depends upon the angle between the baseline and the line of sight to the target.

The telescope, not shown, is under control of azimuth gear I64. As the azimuth gear rotates the telescope is rotated through an equal angle. Vernier I65 is rigidly secured to shaft I66. Gears I61, I63 and I69 are rigidly secured to shaft I66. The ratio of bevelled gears I61 and I10 which engage each other at right angles is such that shaft I1I rotates once for each complete revolution of venier I65. Worm gear I12 is rigidly secured to shaft I1I. The ratio of worm gear I12 and azimuth spur gear I64 which engage is such that gear I64 rotates through one threehundred and siXtieth of a revolution for each revolution of gear I12. The azimuth gear and the telescope therefore rotate through one degree for each complete revolution'of Vernier I65. The

I59 shown in the lower portion of the drawing 7 is also designed to pass current of a different particular one of the fifteen frequencies and to suppress current of the fourteen other frequen:

cies.

The bottom terminal of the output side of each of band-pass filters I20 to I34 is connected by means of conductor I50 to the bottom terminal of winding I5I of transformer I02. The top terminal of each of the top ten band-pass filters I20 to I29 is connected to a different one of the ten terminals of the ten-point switch I52. The top terminal of each of the five band-pass filters I36 to I34 is connected to a. different one of five terminals on ten-point switch I53. The bottom terminals of each of band-pass filters I to I49 is connected to the top terminal of winding I54 of transformer I04. The top terminal of each of band-pass filters I35 to I39 is connected to each of the five remaining terminals of ten-point switch I53. Each of the top terminals of bandpass filters I40 to I49 is connected to a different one of the ten terminals of ten-point switch I55.

Depending upon the position of rotatable arm I56 of ten-point switch I52, the circuit from some one of the ten band-pass filters I20 to I29 will be closed through arm I56 and conductor I51 to conductor I which connects to the top terminal of winding I5I of transformer I02- Depending upon the positionof rotatable arm I59, a path will be closed from some one of filters I30 to I39 through arm I59 and conductor I60 to conductors I58 and I6I. Conductor IOI connects to the 'cured to shaft I16.

azimuth spur gear I64 engages spur gear I13. The ratio of gears I64 and I13 is such that gear I13 rotates thirty-six times for each rotation of gear I64. Gear I13 therefore rotates once for each ten rotations of Vernier I65. Gear I13 is rigidly secured to shaft I14. Rotatable switch arm I59 is also rigidly secured to shaft I14. Rotatable switch arm I59 will therefore rotate through one revolution for each ten revolutions of Vernier I 65. Arm I59. will rotate from any one point on switch I53to the next, while vernier I65 rotates once. This change in position of arm I59 therefore defines one-degree change of the position of the telescope.

Bevelled gear I68 engages bevelled gear I15 at right angles. The ratio is such that gear I15 rotates once for each revolution of gear I68. Gear I15is rigidly secured to shaft I16. Rotatable switch arm I62 of switch I55 is rigidly se- Rotatable switch arm I62 therefore turns through one complete revolution for each revolution of Vernier I65. A change in the position of arm I62 from one point to the next represents a change of a tenth of a degree in the position of the telescope.

Bevelled gear I69. engages bevelled gear I11 at right angles. I11 rotates ten times for each revolution of gear I66. Gear I11 is rigidly secured to shaft I10. Rotatable switch arm I56 is also rigidly secured to shaft I18. Arm I56 will rotate once in onetenth of a degree. The displacement of rotatable arm I56 from one contact to the next succeeding contact corresponds, therefore, 7 to a change in the position of the telescope of onehundredth of a degree.

When rotatable arm I56 engages a particular point on switch I52 alternating current of the particular frequency passed by the corresponding band-pass filter will be impressed across winding I5I' of transformer I02 and induced in winding IOI of transformer I02. The current will be conducted back to the receiving station and impressed through transformer winding 206 on amplifier 2I5. The output ofamplifier 2I5 is connected in parallel to filters 220 to 234 which correspond to filters I20 to I34 at the observing station. The particular frequency which has been selected by switch I52 will be passed through some The gearratio is such that gear.

one filter of band-pass filters 229 to 229 and will be suppressed by all of the others. After passing through the particular filter, current of the particular frequency will be amplified by a corresponding amplifier in the amplifier group 259 to 259.

The output of each one of amplifiers is connected in parallel to a different ten lamps in the display unit 329. Display unit 329 comprises one hundred lamps equally spaced on the circumference of a circle. The lamps are numbered consecutively from to 99. Conductor 359 is connected from amplifier 259 in parallel to the inner terminal of lamps numbered 0, 10, 20, 30, 40, etc. Conductor 35| is connected from amplifier 25I in parallel to the inner terminal of lamps numbered 1, 11, 21, 31, 41, etc. Each of the other eight of the ten conductors 359 to 359 is connected in parallel to the inner terminal of a corresponding group of ten lamps. Depending, therefore, upon the position of the telescope and the contact of switch I52 engaged by arm I56, alternating current will be connected to the inner terminal of a, particular group of ten of the hundred lamps in the display unit 329.

Depending upon the setting of switch I55, alternating current of some particular frequency will be impressed on winding I54 of transformer I94 to identify the particular tenth degree zone in which the target is located at the moment. The current will be induced in winding I93 of transformer I94 and conducted to the receiving station by means of conductors 2I I and 2 I2. It will pass through transformer winding 208 and through amplifier 323 and will be impressed on the input of filters 235 to 249. Some one of filters 249 to 249 will pass current of this particular frequency. All other filters of the group 235 to 249 will suppress current of this particular frequency.

An individual amplifier 265 to 219 is connected to each of filters 235 to 249. An individual detector 285 to 299 is connected in series with each and an individual relay 395 to 3I9 is connected to the output of each of detectors 285 to 299. Current of the particular frequency which has been selected by switch I55 after passing through some one of the band-pass filters 249 to 249 and being amplified by the corresponding amplifier 219 to 219 and detected by the corresponding detector 299 to 299 will operate a corresponding relay of the group 3I9 to 3I9. The operation of the particular relay will connect direct ground through a corresponding contact to the outer terminal of a particular group of ten lamps in the display unit. Thus the operation of relay 3I9 will supply ground through'its contact to the outer terminals of lamps O to 9 in parallel. The operation of relay 3I8 will supply ground through its contact to the outer terminal of lamps 10 to 19 in parallel, etc.

Some particular lamp of the one hundred lamps on the display unit 329 will therefore light to indicate the location of the line of sight to the nearest hundredth of a degree. The manner in which the particular degree is defined Will now be described,

Alternating current of ten of the fifteen frequencies impressed on conductors III and H2 is employed to define the digits in the two righthand positions of the multidigit number corresponding to the observed data. Depending upon the position of the rotatable arm I59 of switch I53, alternating current of some one of the five remaining frequencies selected by filters I 39 to I34, inclusive, will be conducted to the receiving station over conductors 299 and 2 I9, or current of some one of the same five frequencies will be selected by some One of filters I35 to I39 and conducted through switch I53 over conductors 2H and 2 I 2 to the receiving station. Depending upon the transmitting circuit over which the current is transmitted, it will be amplified by either amplifier 2I5 or 323 and selected by some one of band-pass filters 239 to 234 or 235 to 239. It will be amplified by some one of the corresponding amplifiers 260 to 269, detected by some one of detectors 299 to 289, and will operate some one of relays 309 to 399. Depending upon which relay is operated, battery will be connected through a corresponding relay contact to some particular one of the ten conducting segments of distributor 325.

Distributor 325 is equipped with two rotatable arms 325 and 321. The arms are rigidly secured to a rotatable core which is secured rigidly to shaft 329. Shaft 329 is under control of motor assembly 328 and is conditioned to be rotated in either of two directions. Distributor 325 is equipped with a segmented outer ring having ten conducting segments separated by insulators and two individually insulated solid inner conducting rings 339 and 33I. Rotatable arm 321 is equipped with two interconnecting conducting brushes. engages the outer segmented ring. The inner brush engages conducting ring 339. Rotatable arm 326 is also equipped with two interconnecting conducting brushes. The outer brush engages the outer segmented ring. The inner brush Brushes 326 and 321 are angularly spaced so that they will just straddle any segment of the outer ring of distributor 325. Conducting ring 339 is connected by means of conductor 332 to the left-- hand brush of armature 333, the. right-hand brush of which is connected to ground. Conducting ring 33I is connected by means of conductor 335 to the left-hand brush of armature 334, the right-hand brush of which is connected to ground.

A circuit may be traced from grounded battery 349 through the motor field windings 34I to ground. Connected between the brushes of armatures 333 and 334 are antihunting resistances 342 and 343, respectively.

The segments of the outer segmented ring of distributor 325 are numbered from 1 to 10. It will be assumed that relay 39I has been operated and that battery is connected therefore to segment 1 of distributor 325. A circuit may then be traced from battery through the contact of relay 39I, segment 1 of distributor 325, outer brush of rotatable arm 326, inner brush of rotatable arm 326, conducting ring 33I, conductor '335 and armature 334 to ground. In response to this armature 334 will rotate in a counter-clockwise direction, rotating shaft 329 which in turn rotates both rotatable portion of segment 2. Due to the spacing of arms 326 and 321 arm 321 will be rotated simultaneously to a position in which it is stopped just short of segment 1 or at the righthand end of segment 0. Segment 1 will thus be straddled by brushes 326 and 321.

If it is now assumed that relay 390 operates a engages conducting ring 33I..

and armature 333 to ground. In response to this, armature 333 will be rotated in a clockwise direction. Shaft 329 will rotate brushes 32B and 321 in unison in a clockwise direction until brush 321 has moved off segment and engages the righthand end of segment 9. Brush 326 will be rotated simultaneously to the extreme lower portion of segment 1. Segment 0 will thus be straddled by the brushes. It should be clear from the foregoing description of the operation of the apparatus comprising the motor switch that the se ment to which battery is connected will always be straddled by rotatable arms 326 and 321.

Attention is called to the fact that the movement of the telescope is from one degree position to the next higher or neXt lower degree position. As a result of this, when battery has been connected to a particular segment of distributor 325 the movement of the telescope in either of the possible directions through a degree transition will result in the connection of battery to an adjoining segment on distributor 325 in a clockwise or counter-clockwise direction, corresponding to the movement of the telescope. As a. result of this, one or the other of brushes 326 or 3.21 will always be in position to activate armature 333. or 3.34 to move, brushes 326 and 321 into positions, such that one or the other will engage a, segment to which battery will be connected when the position of the telescope is moved forward or. retrcgrcssively into the next degree zone.

Shaft 329 and gear 324, rigidly secured to shaft 329., will occupy a different definite position for each segment to which battery is connected.

Azimuth gear 32.2 engages spur gear 324. The ratio of the gears is thirty-six to one. Gear 324 rotates thirty six times for each revolution. of. gear 322. Gear 324 rotates once for each tendegrcechange of azimuth. Gear 322 rotates once. for each three-hundred-sixty degree change. of azimuth. Gear 322 is rigidly secured to. shaft: 3:80,. A scale numbered from 0' to 360, not: shown, may be attached. to gear or-separat'ely'mounted on shaft 369. A suitable, fixedreferencepoint. will indicate the particular degree position.

It is particularly pointed out thatv the degree switchv is arranged so that it will identify any one; of. ten degree positions within any ten-degree zone. However, the system. isnotlimitedlto' defining positions within. a ten-degree zone only. Any degree position in. the: full three-hundredsixty-degreerange can be defined: by'this' system; Dueto'the arrangement of the degree: recording. mechanism; degree information recorded? is cu. mulative- As shaft 3- 29; and gear 324- are? rotated acomplete rotation will defines a. changexof ten degrees whichwill be. imparted to: azimuth gear 322;. Gear will be movedithrouglr tendegrees for each: revolution of shaft and: gear 324;. For each. of: the three hundred: and. sixty positions of azimuth gearv led at the observing station there will be a corresponding position. or azimuth gear. 322 at thereceivingstation;

Gear ay. be arranged in any convenient" manner so it can be disengagedfrom: gear 322 sc-that gear and gear Hi4 mayibetfixed i n; c-orrespcndir. g positionsat convenient; timeszto' care-for any variation intransmission.

Variable resistance 2M regulates the direct current supplied to amplifier llflqatj the.- observ.-- ing station.

If, it is desired, relays such as; relays 38.0; to; H 9; may, be connected to amplifiers 259130: 259; and; direct, current'may; be supplied toilight the'lampsz in display unit 320;

The display unit may be equipped with a tracking mechanism as it is known in the art to trans fer the observed data to an automatic computing mechanism.

What is claimed is:

1. In a data transmission system, an observing station, a receiving station, a pair of electrical transmission paths interconnecting said stations,

means for coupling said pair of paths to form a phantom circuit, means at said receiving station for impressing on said phantom circuit a plurality of alternating currents of difierent frequencies, means at said observing station for selecting from said plurality alternating current of a particular frequency to define an observation at said observing station, and means at said observing station for impressing said current on a selected one of said paths.

2. In a data transmission system, an observing station, a receiving station, an electrical signal transmission circuit interconnecting said stations, said circuit having a first and a second path, a supply of alternating current of fifteen different frequencies at said observing station, means at said observing station for making three separate selections from among said frequencies to define simultaneously all of the separate parts of any number in the range --rom 0 to 36,000 corresponding to a particular setting of a measuring instrument at said observing station, means at said observing station, responsive to the setting of said instrument, for impressing current of one of a first group of ten of said fifteen frequencies on said first path, means at said observing station, responsive to said setting, for impressing current of one of a second group, different from said first group, of ten of said fifteen frequencies on said second path, means at said observing station, responsive to said setting, for impressing current of one of either of two groups of five of said fifteen frequencies on a selected one of said two paths, and means at said receiving station responsive to the reception of. current of said three frequencies impressed on said paths for indicating said number corresponding to said setting.

3 In a data transmission system, an observing station, a receiving station, a first and a second separate electrical transmission circuit interconnecting said stations, instrumentalities in said system for transmitting signals between said stations to define multidigit numbers corresponding to observed data, said instrumcntalities comprising means for supplying alternating current of fifteen different frequencies, frequencies numbered 1 to 15, to said observing station, means at; said observing. station for selecting a first current. of any one of ten 01 said frequencies, frequencies numbered. 1 to 10, and impressing said first current on said first circuit to define a first portion. of said number, means at said observing station. for selecting a second current of any one of: ten of said frequencies, frequencies numbered 6; to- 15, and: impressing said second current on said second circuit to define a second portion of said number, means at said observing station for selecting a-third. current of any one of five of said frequencies, frequencies numbered 11 to 15 and impressing said"v third current on said first circuit or'for selecting a fourth. current of any one of five of. said frequencies, frequencies numbered 1 to 5, anvil impressing said fourth current on said seccud-circuit, so as todefine a third portion of said number with either said third or said fourth current, dependent on the magnitude of said third portion.

4. In a data transmission system means for impressing alternating current of two different frequencies, selected from fifteen different frequencies, simultaneously on a selected first circuit of a first and second circuit, said circuit depending upon the frequencies of the current selected, and means for impressing an alternatin current of a single frequency, selected from ten of said fifteen frequencies, on said second circuit, simultaneously with the impressing of said current on said first circuit, to define substantially instantaneously three separate digits of a single multidigit number corresponding to an observation at an observing station.

5. A data transmission system for definin all of the digits of a multidigit number simultaneously, two separate transmission circuits and current frequency discriminating means both in said system, means, connected to said discriminating means, for impressing on a first one of said circuits a first alternating current of a particular one of ten selected frequencies, of a first group of fifteen frequencies, to define a first portion of said number, means, connected to said discriminating means for impressing on the second one of said circuits a second alternating current of a particular one of ten selected frequencies of a second group of said same fifteen frequencies, to define a second portion of said number, and means, connected to said discriminating means, for impressing a third alternating current, of a particular one of the five remaining frequencies of said first group, on said first circuit, or of a particular one of the five remaining frequencies of said second group, on said second circuit, to define a third portion of said number.

6. In a data transmission system, an observing station, a receiving station, a first and a second separate electrical transmission circuit interconnecting said stations, means in said system for supplying alternating current of fifteen different frequencies, frequencies numbered one to fifteen, to said observing station, means at said observing station for selecting a first current of any of ten of said frequencies, frequencies numbered one to ten, and impressing said first current on said first circuit to define a first portion of a multidigit number corresponding to a measurement at said observing station, means at said observing station for selecting a second current of any of ten of said frequencies, frequencies numbered six to fifteen and impressing said second current on said second circuit to define a second portion of said number, and means at said observing station for selecting a third current of any of the five frequencies, frequencies numbered eleven to fifteen, and impressing it on said first circuit, or for selecting a third current of any of the five frequencies, frequencies numbered one to five, and impressing it on said second circuit, to define a third portion of said number.

7. In a data transmission system, an observing station, a receiving station, a first and a second electrical transmission path interconnecing said stations, means in each of said paths for selectively conducting current of any of fifteen different frequencies between said stations, a first selecting and transmitting means, responsive to a measuring means, at said observing station for selecting and transmitting a current of a particular one of the ten lowest frequencies of said fifteen frequencies through said first path, a second selecting and transmitting means, responsive to said measuring means, at said observing station for selecting and transmitting current of a particular one of the ten highest frequencies of said fifteen frequencies through said second path, and a third selecting and transmitting means, responsive to measuring means, at said observing station for selecting and transmitting current of a particular one of the five highest of said fifteen frequencies through said first path or current of a particular one of the five lowest of said fifteen frequencies through said second path, to define substantially instantaneously, three separate portions of a multidigit number, corresponding to a measurement at said observing station.

8. In a data transmission system, means for separating currents of 12 different frequencies into currents of two different first groups each of a frequencies, means for selecting current of one of said at frequencies in each of said groups to define each of two portions of a multidigit number, means for separating current of said 11 frequencies into currents of two different second groups each of (n-a) frequencies, means for selecting current of one of said (rt-d) frequencies in one or the other of said groups of (12-11) fre quencies to define a third portion of said multidigit number an observing station, a receiving station, a first and a second transmission path interconnecting said stations, means at said observing station for impressing said selected current of one of said a frequencies of one of said first groups on said first path, means at said observing station for impressing said selected current of one of said a frequencies of the other of said first groups on said second path and means at said observing station for impressing said ,selected current of one or the other of said groups of (n-a) frequencies on said first path or on said second path depending upon the frequency selected.

FRED J. SINGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,232,499 Clausen July 10, 1917 1,245,417 Adams Nov. 6, 1917 1,116,497 Friedrick Nov. 10, 1914 2,081,634 Stoddard May 25, 1937 1,889,597 Fitz Gerald Nov. 29, 1932 2,039,405 Green et a1 May 5, 1936 2,117,580 Snavely May 17, 1938 FOREIGN PATENTS Number Country Date 464,544 Germany Aug. 20, 1928 

